Add hierarchical backprojection

About

Another tentative at integrating HBP - previous iteration was !315 (closed)

To do

• Integrate HBP
• Unit test
• Integrate in pipeline
• Update changelog/documentation
• End-to-end reconstruction test

Notes

Works (unit-tested):

• Reconstruction of even and odd shape
• Half-tomo
• CoR (always uses centered_axis=1)
• clip_outer_circle
• axis_corrections
• scale_factor

Works (not unit-tested):

• Padding mode and filter_cutoff (handled by SinoFilter)

Not supported:

• centered_axis=False
• ROI reconstruction